1. Field of the Invention
The present invention relates to joining of aluminum metal bodies to each other, and in particular, to coating of one of those aluminum metal bodies to be joined to one another with aluminum alloy brazing filler metal.
2. Description of the Prior Art
In assembling of a product having a plurality of aluminum metal bodies, elements or parts, those aluminum metal parts are often connected or joined to one another by brazing.
In production of, for example, a serpentine type refrigerant evaporator as disclosed in U.S. Pat. Nos. 4,350,025 and 4,353,224, corrugated fin units and an inlet and an outlet header pipes are fixedly joined to a serpentine-anfractuous flat metal tube.
The corrugated fin units, the flat tube, and the header pipes are usually made of aluminum alloys. For example, the flat tube is made of an aluminum alloy AA (Aluminum Association in U.S.A.) 1050. Since aluminum alloy brazing filler metal is necessary to join aluminum metal parts to each other, each fin unit is usually made of an aluminum brazing sheet which has a core metal of, for example, AA 3003 with a cladding of an aluminum alloy brazing filler metal such as AA 4343, 4045, or 4047. Each header pipe is also made of a similar aluminum brazing sheet by the use of an electric resistance welding tube mill.
The fin units, flat tube and header pipes are preassembled, and are heated in a brazing furnace to a brazing temperature of about 600.degree. C. Then, the filler metals on surfaces of the fin units and header pipes melt and flow so that the fin units and header pipes are joined to the flat tube by brazing.
An aluminum brazing sheet is usually made by putting a core aluminum metal piece between two pieces of the filler metal and rolling them together.
The aluminum brazing sheet is hard because the filler metal has a comparatively high hardness, and therefore bending of the brazing sheet is not so easy but difficult. Therefore, it is not easy to form the corrugated fin units and the header pipes from aluminum brazing sheets. This is a factor of the high cost of the evaporator, in addition to another factor that the aluminum brazing sheet per se is expensive.